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Asphalt is one of the primary ingredients in roofing shingles. Its purpose is to provide the waterproofing integrity for the roof. Secondarily, the asphalt holds the colored granules in place and contributes 10 the overall strength of the shingles. Asphalt, which is derived from petroleum, contains the oils that provide ductility and pliability to the shingles. During the lifetime of the shingles these oils begin to rise to this surface, where they are washed away by rainwater. In an attempt to restore equilibrium, new oils surface and the washing process continues. Also, the intense heat of the roof oxidizes or hardens the asphalt over time.

Key Danger Signals:

  • Missing, cracked, curled or blistered shingles.
  • Excessive energy costs.
  • Dark. dirty looking" areas on your roof.
  • Stains on interior ceilings and walls; mold or mildew growth.
  • A leak in the attic.
  • Exterior decay, sheathing, and/or siding.
  • Blistering or peeling interior or exterior paint.

You may ask yourself, "What can I expect my roof to look like as the aging process takes place?"

One of more of the following conditions may occur over time:

Curling: As the asphalt hardens over time, the granules which were once securely embedded begin to break away. Occasionally you may have seen the colored granules in your gutters. Also, as this hardening advances, the asphalt layers begin the shrink. Of course, all of this is occurring at a microscopic level and is not something which will be noticeable on a daily basis. As the asphalt layer shrinks, it is being countered by the shingle reinforcement, which resists shrinking. We not have a situation in which the top and bottoms coatings are shrinking and the reinforcement is remaining stable. As a result, the edges of the shingle may begin to curl over time. In addition, organic shingles may exhibit signs of curling which might be considered excessive, however, this is not a manufacturing defect and would be considered part of the normal weathering process of organic shingles.

Surface Cracking: Another manifestation of the normal aging process may be the development of surface cracks. For example, as the flexible oils of the asphalt are depleted due to heat, the shingle becomes more brittle, to the point where surface cracking may appear. The stresses created by thermal shock and the movement of the roof deck also increase the likelihood of surface cracking.

Blisters: During the course of natural weathering, small bubble-like raised spots like blisters may appear on the surface of the shingles. These blisters may be small and pea-sized or as large as a quarter. The blisters may be open, Exposing the asphalt, or closed. Blisters frequently result when minimum ventilation requirements are not met.

Staining: Finally, over a period of time, shingles may develop dark brown or black streaks that are sometimes mistaken for soot, dirt, moss or tree droppings. In actuality, this discoloration may be caused by algae growth. Although most roofing systems are susceptible to algae discoloration, it is most readily visible on white or light-colored shingles.

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